Lubrication system for fine mechanisms



D 1965 M. K. BERNETT ETAL 3,

LUBRICATION SYSTEM FOR FINE MECHANISMS Filed Nov. 19, 1963 FIG? INVENTORS MAR/ANNE K. BERNETT WILLIAM A. Z/SMAN ATTORNEYS United States Patent 3,225,866 LUBRICATION SYSTEM FOR FINE MECHANISMS Marianne K. Bernett, Washington, D.C., and William A. Zisman, Silver Spring, Md., assignors to the United States of America as represented by the Secretary of the Navy Filed Nov. 19, 1963, Ser. No. 324,897 Claims. (Cl. 184-1) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a system for the lubrication of fine mechanisms, more particularly to a surface modification of parts of fine mechanisms to enable the use therein of lubricating oils of the spreading type.

It has long been recognized in the lubrication of fine mechanisms which are normally enclosed, such as watches, clocks and many meters, that the oil must remain in drop form at the area of lubrication for long periods of time.

Until about thirty years ago, nonspreading clock oils had been mainly obtained from porpoise jaw oil, black fish oil, neats foot oil, bone oils and olive oil by various refining procedures which were more or less considered as trade secrets. The principal difficulties with these oils were their tendencies to evaporate, to thicken and to deposit gums. Batches of oil from the like source often were two variable in nonspreading and stability properties. Effective product was rare and oil specifications were inadequate.

Shortly before the middle of the present century research was started on clock oils and their synthesis to the end of increasing the supply of clock oils and countering increasing cost of the source. The research culminated in the development of a useful synthetic clock oil. Despite this success, it Was still desired to improve the lubricant in respect to lower vapor pressure, better oxidation stability, lower freezing point and lower cost. If lubricating oils of the spreading type could be enabled to be used as clock oils many of the aforesaid improvements could be attained, as well as an enlarged supply of oils for the lubrication of clock, watch and the like fine mechanisms.

It is an object of the present invention to assist the use of lubricating oils of the spreading type in the lubrication of fine mechanisms, more especially in those which are enclosed, such as clocks, Watches and indicating meters, whereby to take advantage of valuable properties of lubricating oils of the spreading type and to Widen the base of supply of clock oils. It is also an object to provide fine mechanisms with means for intercepting spread of lubricating oils of the spreading type from areas of lubri-- cation therein whereby to contain them at such areas.

The above and other objects are accomplished following our invention through the provision on parts to be lubricated in fine mechanisms of a band of a thin film of a fluorinated polymer of a monomer which may be 1H,lH-pentadecafluorooctyl methacrylate or Z-(N-propylperfluorooctane sulfonamido)ethyl acrylate which is arranged to intercept lubricating oil spreading from the area of lubrication of the parts.

We have found that a thin film of a fluorinated polymer as defined above encircling a drop of lubricating oil of the spreading type on a solid surface will prevent spreading of the oil over the solid surface and that this system can be effectively employed to enable the use of oils of the spreading type for the lubrication of parts of fine mechanisms.

The invention will be more readily understood from the description which follows when read in conjunction with the accompanying drawing in which several embodiments of the invention are shown by way of illustration. The parts and clearances between parts are shown in greatly exaggerated dimensions in the drawing for purposes of clarity in illustration.

In the drawing:

FIGURE 1 is a View, partly in section, of a bearing and shaft of the pivot type in assembled arrangement and provided with an oil spread barrier following the present invention,

FIGURE 2 is a view, partly in section, of a bearing and shaft of the journal type in assembled arrangement and provided with an oil spread barrier following the present invention, and

FIGURE 3 is a view, partly broken away, of an escapement for a watch provided with an oil spread barrier following the present invention.

Referring to FIGURE 1 of the drawings, the assembled pivot bearing 1 and shaft 2 are of conventional design. The shaft 2 is arranged for rotation in frictional contact with the bearing surface 3 at the apex of the conically shaped well 4 by means of the pivot 5 on the gudgeon 6. Coated on the face of the bearing at 7 and encircling the well 4 near its perimeter is a thin film of a fluorinated polymer as defined above. A band 8 of a thin film of the fluorinated polymer is also coated on and encircles the shaft 2 about the gudgeon 6 a slight distance above the pivot portion 5.

In operation of the pivot bearing and shaft assembly described above, a drop 9 of a lubricating oil of the spreading type, e.g., a refined mineral oil of low viscosity, placed at the area of lubrication of the parts will be contained at the area by means of the action of the rings 7 and 8 of the fluorinated polymer which will intercept oil which tends to spread from the area of lubrication and over the surface of the bearing 1 and shaft 2.

FIGURE 2 shows the application of oil barrier films of the invention to a parts assembly of the type commonly used in watch mechanisms. The assembly comprises an annular jewel bearing 10 and a metal staff 11 having a beveled shoulder to a journal 12 which extends through the bearing for rotation in frictional contact with the bearing surface 13. The bearing 10 is coated on each of its faces with a thin film 14, 14 of a fluorinated polymer as defined above which is located near and encircles the respective end of the bearing surface 13. The staff 11 is coated and encircled with a pair of spaced thin films 15 and 16 of the fluorinated polymer. The film 15 is located on the bevel shoulder of the staff and the film 16 on the journal 12 at a distance below the film 15 which is slightly greater in length than the length of the bearing surface 13 and arranged to include the bearing surface between them.

In operation of the assembly as shown in FIGURE 2, a drop 17 of a lubricating oil of the spreading type applied to the bearing surface 13 will be prevented from spreading away from'the area of lubrication by the intercepting rings 14, 14 of the fluorinated polymer on the annular bearing 10 and by the intercepting rings 15 and 16 of the fluorinated polymer on the staff 11 whereby the oil may be contained at the area of lubrication for long periods of time.

Oil barrier films may be applied following the invention to fine movements which are assemblies of parts which move in a slow, intermittent fashion as illustrated by the detached lever escapment for a watch shown in FIGURE 3. The escapement as shown comprises an escape wheel 18 provided with teeth 19 which are engaged by the pallet stones 20 carried by the fork 21. A thin film 22 of a fluorinated polymer as defined ElJbOVB is coated on and encircles the shank portion of the teeth 19 near the area of engagement of the teeth with the pallets 20. A similar thin film 23 of the fluorinated polymer is coated on and encircles the pallet stones 20 near the area of their contact with the wheel teeth 19. A drop of a refined-lubricating oil of the spreading type applied to the pallet stone or to the teeth will be limited to the general area of lubrication of the teeth and pallets by the intercepting action of the films 22 and 23.

The oil barrier films of the fiuon'nated polymers as defined above can be readily laid down on the surface of parts of fine mechanisms which are to be lubricated from a solution of the fluorinated polymer in an appro' priate solvent such as xylene hexafluoride or benzotrifluo' ride which, after slow evaporation, leaves a suitable coating on the metal or jewel surface. The thickness of the fluorinated polymer films is not critical and may be varied by adjusting the concentration of the fluorinated polymer in the solvent solution. A fine camel hair brush can be used to paint bands of the fluorinated polymer of any desired width on the parts to define intercepts o1 barriers which surround the oil on the parts and contain it at the area of lubrication.

The fluorinated polymers as defined herein have a low surface energy by virtue of which films of the polymers are effective to prevent spreading on a solid sur face of almost any of the known lubricating oils of the spreading type, for example, petroleum oils, aliphatic diester oils, e.g., bis (Z-ethylhexyl) sebacate, and poly oxyethylene ether oils (Ucon oils). The fluorinated polymers herein defined have a critical surface tension of wetting at 25 C. which is in the range of from about 10.5 to 11 dynes per cm. Any oil or liquid which has a surface tension greater than the critical surface tension of Wetting of the fluorinated polymers will not spread on a film of the polymers. In general, the surface tension of the various known lubricating oils of the spreading type is greater. The oil will spread on the solid surface, for example, steel, brass or synthetic sapphire, to the ring of the fluorinated polymer film but will not pass this barrier.

While the invention has been described herein with reference to certain specific embodiments thereof, it is to be understood that such are intended by way of illustration and not in limitation except as may be defined in the appended claims.

What is claimed is:

1. In a mechanical assembly of fine parts comprising a part arranged for movement in frictional contact with another part,

means for containing a lubricating oil of the spreading type at the area of frictional contact between said parts,

including a thin low surface energy film of a polymer of a monomer of the group consisting of 1H,1H- pentadecafluorooctyl methacrylate and 2-(N-propylperfluoro-octane sulfonamido)ethyl acrylate coated on each of said parts near the area of frictional contact therebetween and arranged to intercept oil spreading from said area.

2. In a mechanical assembly of fine parts comprising a bearing and a shaft having a gudgeon arranged for rotation in said bearing in frictional contact therewith,

means for containing a lubricating oil of the spreading type at the area of frictional contact of said bearing and shaft including a thin low surface energy film of a polymer of a monomer of the group consisting 1H,1H-pentadecafiuorooctyl methacrylate and 2-(N-propylperfiuorooctane sulfonamido)ethyl acrylate coated on said ibearing and said shaft near the area of frictional contact therebetween and arranged to intercept oil spreading from said area.

3. In a mechanical assembly of fine parts comprising an annular bearing and a shaft having a journal arranged, for rotation in said bearing in frictional contact therewith,

means for containing a lubricating oil of the spreading type at the area of frictional contact of said bearing and shaft including a thin low surface energy film of a polymer of a monomer of the group consisting of 111,111- pentadecafluorooctyl methacrylate and 2-(N-pr0pyl perfluorooctane sulfonamido)ethyl acrylate coated on said bearing and said shaft near the area of frictional contact therebetween and arranged to intercept oil spreading from said area.

4. A mechanical assembly of fine parts comprising a pivot bearing and a shaft having a pivot arranged for rotation in said bearing in frictional contact therewith,

a thin low surface energy film of a polymer of a monomer of the group consisting of lH,lH-pentadeca fluorooctyl methacrylate and 2-(N-propylperfiuorooctane sulfonamido) ethyl acrylate coated on said bearing, near and encompassing the bearing surface thereof and on and encircling said shaft near the pivot thereof.

5. A mechanical assembly of fine parts comprising an annular bearing and a shaft having a journal extending through said bearing and arranged for rotation in frictional contact with the bearing surface,

a thin low surface energy film of a polymer of a monomer of the group consisting of 1H,lH-pentadecafiuorooctyl methacrylate and Z-(N-propylperfluorm octane sulfonamido) ethyl acrylate coated on each face of said bearing, near and encompassing the respective end of the bearing surface,

and on and encircling said shaft in bands which are spaced apart a distance slightly greater than the length of said bearing surface and positioned to include said bearing surface therebetween when said bearing and shaft are in the assembled condition.

References Cited by the Examiner UNITED STATES PATENTS 2,693,458 11/1954 Olson 26031.2 3,077,368 2/1963 Pignone 58140 X 3,080,703 3/1963 Body 58140 LAVERNE D. GEIGER, Primary Examiner.

MILTON KAUFMAN, Examiner.

H. S. BELL, Assistant Examiner. 

1. IN A MECHANICAL ASSEMBLY OF FINE PARTS COMPRISING A PART ARRANGED FOR MOVEMENT IN FRICTIONAL CONTACT WITH ANOTHER PART, MEANS FOR CONTAINING A LUBRICATING OIL OF THE SPREADING TYPE AT THE AREA OF FRICTIONAL CONTACT BETWEEN SAID PARTS, INCLUDING A THIN LOW SURFACE ENERGY FILM OF A POLYMER OF A MONOMER OF THE GROUP CONSISTING OF 1H,1HPENTADECAFLUOROOCTYL METHACRYLATE AND 2-(N-PROPYLPERFLUOROOCTANE SULFONAMIDO)ETHYL ACRYLATE COATED ON EACH OF SAID PARTS NEAR THE AREA OF FRICTIONAL CONTACT THEREBETWEEN AND ARRANGED TO INTERCEPT OIL SPREADING FROM SAID AREA. 